The present invention relates to an improved method and system for detecting a failure of a compressed air consumer circuit in an electronic compressed air system for vehicles.
Multi-circuit protective valves are known that divide an energy supply into several mutually independent consumer circuits and, in the event of failure of one consumer circuit, for example by line rupture, maintain a minimum pressure in the intact circuits. If a defect allowing more air to be lost than can be resupplied by the compressor occurs in a service-brake circuit, the pressure in the service-brake circuit drops mutually until the pressure reaches the closing pressure of the valve. The pressure in the defective circuit continues to drop, whereas the closing pressure is maintained in the intact circuits. While the pressure in the defective circuit continues to drop, the circuits that are still intact can be refilled by the compressor until the opening pressure of the defective circuit is reached. A dynamic equilibrium is established in which the delivered compressed air can supply the circuits that are still intact (as well as secondary consumer circuits), although at the same time air is being lost via the defect. During compressed air consumption of limited duration, as in the case of heavy braking, momentary dynamic pressure collapses occur which do not correspond to the reservoir pressures of the individual consumer circuits. This behavior is much more pronounced in circuits without compressed air reservoirs than in circuits with compressed air reservoirs. A disadvantage of the known multi-circuit protective valves is that they react to such dynamic pressure collapses and shut off the circuit in question if such circuit has a low pressure level. The occurrence of such momentary dynamic pressure collapses, therefore, leads, at low pressure level, to premature shutoff of circuits, even though the respective pressure at the end of the event (i.e., at the end of the pressure collapse) would still be higher than the closing pressure.